textproduct: Albany

UPDATE

As of 7:20 PM EST...Quick adjustment to PoPs, QPF, and snow amounts to reflect band of at times moderate snow that is tracking from the Mohawk Valley towards the Saratoga Lake George region and eventually southern VT. NY thruway webcams show some areas in the Mohawk Valley picked up half inch to inch of snow under this band. However, this band is moving into a very dry airmass, with the 00z KALY sounding showing a lot of low-level dry air that needs to be eroded before snow reaches the ground. So, expecting lighter snowfall amounts from the Hudson Valley eastward. The snow showers with this first clipper are still expected to dissipate within the next few to several hours, with a lull through the rest of the night before another round of snow arrives tomorrow morning. Please see previous discussion below for more details...

SYNOPSIS

After a chilly Tuesday, expecting a quick moving clipper to usher in widespread snow starting late tonight through the day tomorrow. A period of moderate to heavy snow is likely in the higher terrain areas through early afternoon leading to slippery travel while marginal temperatures likely keeps snow accumulations light elsewhere. Then, much colder temperatures and gusty winds arrive for Thursday with potential for additional snow accumulations from lake effect and upslope snow.

SHORT TERM /THROUGH THURSDAY NIGHT/

Key Messages:

- Winter Storm Watches have been upgraded to Winter Storm Warnings for the western and southern Adirondacks from 4AM Wednesday through 7AM Thursday.

- Winter Weather Advisories have been issued for the southern Greens, the Upper Hudson Valley, and portions of the eastern Catskills from 4AM Wednesday to 1AM Thursday where 3 to 6 inches of snowfall is expected. Slippery travel for the Wednesday morning and evening commute is likely.

- There is 30 to 60% chance for wind gusts to exceed 35mph on Thursday as well as 20 to 40% chance for at least 2 inches of snow in the western Mohawk Valley, southern Greens, and southern Adirondacks from lake effect and upslope snow. The combination of gusty winds and freshly fallen snow can also result in blowing/drifting snow on Thursday.

Discussion:

A series of clipper disturbances will impact portions of the Northeast tonight through tomorrow. The first is set to arrive this evening and while the sfc low is displaced well to our north and west tracking through the Upper Midwest, a quick push of warm air and moisture advection will lead to a period of steady snow in the southern Adirondacks and southern Greens mainly from 00 to 06 UTC. Upsloping along the south facing slopes of the Adirondacks looks to enhance QPF amounts tonight leading to a quick 1 to 2 inches of snow. Otherwise, temperatures tonight will likely be coldest at the beginning of the night tonight in the 20s and then stay steady or even rise a few degrees overnight as clouds thicken/lower.

Our next stronger and quick moving clipper will arrive right on its tail late tonight as it tracks through the Great Lakes and up the Saint Lawrence River Valley through the day tomorrow. Given its westerly track, a period of strong isentropic lift starting 09 - 15 UTC tomorrow morning will lead to snow quickly breaking out over the southern Adirondacks, Mohawk Valley, Upper Hudson Valley and northern/eastern Catskills. Upsloping enhancements along the south facing slopes of the southern Adirondacks will quickly promote moderate to heavy snowfall rates developing shortly after snow begins with the HREF showing 50 to 80% chances for hourly snowfall rates to exceed 1" with even 20 to 30% chance for 2"+ snowfall rates through early afternoon. Moderate to heavy snowfall rates 0.5-1" per hour even spill into the foothills of the Adirondacks and into parts of the Upper Hudson Valley and southern Greens which can lead to slippery travel for the morning commute. Further south and east, temperatures will be cold enough to support all snow but forecast soundings show the thermal profiles quickly moderating in response to the strong southerly winds/warm air advection so snow to liquid ratios look to be under climo ranging 7-10:1. This we likely result in a wetter type of snow with a reduced snow accumulation efficiency. Therefore, our current forecast only shows coatings up to 2 inches for the rest of eastern NY and western New England and there is less than a 20% chance for snowfall amounts to exceed 2 inches. The highest chance for snow to accumulate in these areas will be through early afternoon as temperatures continue to slowly warm into the mid-30s thereafter, making it more difficult for snow to accumulate. Even still, travels should drive carefully and allow extra time to their destination as the recent stretch of cold weather means the ground will be plenty cold and any untreated wet surfaces can quickly turn slippery/icy. Latest forecast shows 7 to 12 inches for the southern Adirondacks most of which falls through the day Wednesday so that was certainly enough confidence to warrant winter storm warnings with winter weather advisories in the western Mohawk Valley, Upper Hudson Valley, southern Greens and portions of the eastern Catskills where 2 to 5 inches is expected. Locally higher amounts 5 to 8 inches in the southern Green Mountains of southern VT.

By late Wednesday afternoon into the evening, the warm sector and strongest isentropic lift escapes to our east with a dry slot wrapping into the region. This will reduce the coverage of snow (or rain/mix in valley areas) for the evening hours as enter in a bit of a lull. However, shortly after Midnight, the main cold front and trough axis swings through from west to east with winds quickly shifting to the west-northwest and turning breezy as another chilly Canadian air mass surges eastward. Additional snow showers are possible with this front with upslope snow developing in the southern Adirondacks. Otherwise, it will turn chilly again by early Thursday morning as many drop into the low to mid 20s with even teens in higher terrain areas.

Thursday remains chilly and blustery as strong cold air advection continues through the day as our clipper deepens in southern Quebec. Forecast soundings show deep boundary mixing ensuing as the colder Canadian air pours into the region with the top of the mixed layer even reaching 40-50kts. Latest probabilistic guidance shows 30 to 60% chance for wind gusts to exceed 35mph with the highest values down the Mohawk Valley, Capital District into western MA/southern VT. While there is low confidence that we will need wind advisories, there is a strong signal that lake effect and upslope snow showers will develop on Thursday as the parent closed cyclone tracks through Quebec and pushes into northern New England. Once the closed low pushes to our east by midday, guidance shows lake bands becoming better organized off Lake Ontario as strong west- northwest winds flow over the long fetch of the lake. The set-up at 500hPa even hints at the potential for a multi-lake connection but there seems to be higher confidence for a multi- lake band to form off Lake Erie and be directed into northern PA. We will continue to monitor trends as the RGEM shows the potential for a single lake band to track into portions of the Mohawk Valley and northern Catskills midday into the afternoon on Thursday. Despite uncertainly in the exact placement of any lake bands, we will also need to monitor upslope snow in the western Adirondacks, southern Greens, western MA and Taconics late Thursday P.M into Thursday night as flow becomes more westerly. Given blustery winds and freshly falling snow, blowing snow can also reduce visibility and recover any cleared surfaces. Latest guidance shows a 30 to 50% chance for at least 2 inches of snow from 7AM Thurs to 7AM Fri in the western Mohawk Valley and western Adirondacks with a 10% chance in the southern Greens, Taconics and western MA. Depending on how trends shift with the lake effect and upslope snow, additional winter weather advisories may needed.

LONG TERM /FRIDAY THROUGH TUESDAY/

Key Message:

- High confidence in below normal temperatures continuing, along with chances for light snow or snow showers.

Discussion:

It will remain chilly into Friday as weak surface ridging builds overhead on Fri promoting dry conditions, although a westerly flow aloft can support lingering light lake effect snow showers in the W. Adirondacks and W. Mohawk Valley. Then, an upper level low and large scale trough dig across the Great Lakes and SE Canada Saturday night into Sunday which could result in a brief window for cyclogenesis along/near the mid Atlantic coast early Sunday. At this time guidance is showing potential for development, but it may occur just to our east depending on when the trough takes on a negative tilt. This could spread some light snow into at least parts of the area. Will continue to monitor trends.

The upper trough settles into the Northeast Sun into Mon, with another Arctic air mass building in. So temperatures should be well below normal again during this time. 850 mb temperature anomalies from the NAEFS are forecast to be -1 to -2 STDEV. There will be some wind at least through Sun night with high pressure to the west, so wind chills could be below zero across much of the area. High pressure builds in on Mon with winds diminishing, but temperatures remaining cold.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

Through 00z Thursday...Flying conditions are currently VFR at all terminals as of 6:40 PM EST. However, a clipper system this evening will bring some snow showers to ALB/GFL/PSF within the first few hours of the TAF period. At GFL, IFR vsbys will be possible, but for ALB/PSF expecting mainly MVFR vsbys. Not expecting any snow showers at POU. Outside of these snow showers, mainly VFR conditions expected tonight with BKN to OVC mid and high clouds.

Tomorrow, a stronger clipper system brings widespread snow, possibly changing to rain at POU tomorrow afternoon and mixing with rain at ALB tomorrow evening. Have used tempo groups at ALB/GFL where confidence is higher in the start time, and prob30 groups at POU/PSF where start time is a couple hours later, and confidence in exact start time is also lower. Once snow begins, IFR to possibly LIFR vsbys and MVFR to IFR cigs expected. Exception is at POU where low-end MVFR conditions are expected once the snow changes to rain tomorrow afternoon. Precip becomes more showers with some slight improvements to vsbys at GFL/ALB/POU tomorrow evening, but cigs remain IFR at ALB/GFL and low-end MVFR at POU. Snow and IFR or lower vsbys and cigs continues through the end of the TAF valid period at PSF.

Winds tonight will generally be at 5-10 kt from the S/SE with gusts up to 15-20 kt at PSF and ALB. Have also continued mention of LLWS for the first several hours of the TAF period with 35-45 kt low- level jet from the S/SW at 2000 ft. Winds tomorrow increase through the morning to 10-15kt, with gusts of 15-20 kt at POU/GFL and to around 25kt at ALB/PSF. Low-level jet also strengthens again to 40- 50 kt from mid-morning through early evening, so have re-introduced LLWS during this timeframe. For ALB/GFL/POU, wind gusts diminish to around 15kt and LLWS concerns subside tomorrow evening.

Outlook...

Wednesday Night: Moderate Operational Impact. Chance of RA. Thursday: Low Operational Impact. Breezy. Slight Chance of SN. Thursday Night: Low Operational Impact. Slight Chance of SN. Friday: No Operational Impact. NO SIG WX. Friday Night: Moderate Operational Impact. Chance of SN. Saturday: Moderate Operational Impact. Chance of SN.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...Winter Storm Warning from 4 AM Wednesday to 7 AM EST Thursday for NYZ032-033-082. Winter Weather Advisory from 4 AM Wednesday to 1 AM EST Thursday for NYZ038-041>043-063-083. MA...None. VT...Winter Weather Advisory from 4 AM Wednesday to 1 AM EST Thursday for VTZ013-014.